Java/2D Graphics GUI/Transparent

Determining If an Image Has Transparent Pixels

<source lang="java"> import java.awt.Image; import java.awt.image.BufferedImage; import java.awt.image.ColorModel; import java.awt.image.PixelGrabber; import javax.swing.ImageIcon; public class Main {

 public static void main(String[] argv) throws Exception {
   Image image = new ImageIcon("a.png").getImage();
   if (image instanceof BufferedImage) {
     BufferedImage bimage = (BufferedImage) image;
     System.out.println(bimage.getColorModel().hasAlpha());
   }
   PixelGrabber pg = new PixelGrabber(image, 0, 0, 1, 1, false);
   try {
     pg.grabPixels();
   } catch (InterruptedException e) {
   }
   ColorModel cm = pg.getColorModel();
   System.out.println(cm.hasAlpha());
 }

}

 </source>   

Draw ten rectangles with different levels of transparency

<source lang="java"> import java.awt.AlphaComposite; import java.awt.Color; import java.awt.Graphics; import java.awt.Graphics2D; import javax.swing.JFrame; import javax.swing.JPanel; public class TransparentRectangles extends JPanel {

 public void paint(Graphics g) {
   super.paint(g);
   Graphics2D g2d = (Graphics2D) g;
   for (int i = 1; i <= 10; i++) {
     g2d.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER, i * 0.1f));
     g2d.fillRect(50 * i, 20, 50, 50);
   }
 }
 public static void main(String[] args) {
   JFrame frame = new JFrame("Transparent Rectangles");
   frame.add(new TransparentRectangles());
   frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
   frame.setSize(600, 100);
   frame.setVisible(true);
 }

}

 </source>